This DIY Strip Light Stair Lighting Design and Install over at Speedy Signals looks nice. The project uses a ATmega328P which is very common in the Arduino scene. The microcontroller interfaces with some shift registers to power the lights. Some 2N7000 mosfets are used to drive the actual LED lights. By using the Arduino ShiftPWM library he is able to have individual control of all the steps. Beam sensors were the first idea but motion sensors were eventually used.